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EP0699323A1 - Analyse de formes d'ondes cardiaques - Google Patents

Analyse de formes d'ondes cardiaques

Info

Publication number
EP0699323A1
EP0699323A1 EP94915662A EP94915662A EP0699323A1 EP 0699323 A1 EP0699323 A1 EP 0699323A1 EP 94915662 A EP94915662 A EP 94915662A EP 94915662 A EP94915662 A EP 94915662A EP 0699323 A1 EP0699323 A1 EP 0699323A1
Authority
EP
European Patent Office
Prior art keywords
vlp
attractor
value
fractal dimension
parameter
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP94915662A
Other languages
German (de)
English (en)
Inventor
Omar Jacinto Escalona
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BTG International Ltd
Original Assignee
BTG International Ltd
British Technology Group Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by BTG International Ltd, British Technology Group Ltd filed Critical BTG International Ltd
Publication of EP0699323A1 publication Critical patent/EP0699323A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
    • A61B5/316—Modalities, i.e. specific diagnostic methods
    • A61B5/318—Heart-related electrical modalities, e.g. electrocardiography [ECG]
    • A61B5/339—Displays specially adapted therefor
    • A61B5/341—Vectorcardiography [VCG]

Definitions

  • This invention relates to the analysis of heart waveforms and more particularly to the heart waveform represented by the measurement known as the Ventricular Late Potential (VLP).
  • VLP Ventricular Late Potential
  • the invention provides a method of analysing Ventricular Late Potential (VLP) including determining a parameter related to the complexity of the VLP as a parameter for clinical evaluation.
  • VLP Ventricular Late Potential
  • VLP Ventricular Late Potential
  • the VLP attractor is that in three dimensional voltage space, the voltage being ECG measurements.
  • the geometrical realisation of the attractor which need not be carried out to perform the invention, may be considered as a path in phase space defined by ECG voltages in three orthogonal directions.
  • the method may include an approximation to the fractal dimension of the attractor as the quotient of log(L)/log(DD), where L is the total length of the attractor and DD is the spheric extent diameter of the attractor.
  • the approximation may be produced by the application of an algorithm, conveniently in the form of a flow chart.
  • the method may include assessing the ECG signals to define VLP onset and offset points.
  • the assessment of the ECG signals may include signal-averaging and high-pass filtering and the taking of the absolute value of the filtered output.
  • the onset is defined as the vector magnitude combination exceeding a chosen mean or peak voltage. This may be 40 micro volts mean or 48 microvolts peak (mean ⁇ 20%).
  • the offset is defined as the mean voltage exceeding the mean noise level plus three times the standard deviation of the noise sample.
  • a fractal dimension in excess of 1.30 may be selected as the value indicating a risk of sudden cardiac death positive (SCD+) condition.
  • the fractal dimension may be provided as a display or other output.
  • a particular form of amplifier may be employed including three operational amplifiers with a high gain in an early front end stage to minimise noise over a controlled bandwidth, which may be 0.1 to 1200Hz, and low crosstalk, which may be below -90dB.
  • Spectral analysis of VLP may be performed to produce an assessment based on a dlsrete Hartley transform (DHT) vector spectrum by summing amplitude components between -f 1 to -f 2 and +f£ to +f ⁇ where f ] Is a number larger than f 2 .
  • DHT dlsrete Hartley transform
  • Figure 1 is a diagram of electrode positions on the front, sides and back of a human torso
  • Figure 2 is a flow chart for an algorithm for computing the fractal dimension of an attractor
  • Figure 3 shows equations useful in practicing the invention
  • Figures 4 and 5 are each the representation of an attractor
  • Figures 6a, 6b, 7 and 8 are tables of results of measurements according to the invention
  • Figures 9 and 10 each show a DHT vector spectrum
  • Figure 11 shows a circuit diagram of an amplifier for ECG signals.
  • Figure 1 shows the position of electrodes in the conventional bipolar orthogonal XYZ lead system.
  • the pairs of electrodes (+X, -X) (+Y, -Y) and (+Z, -Z) each relate to an orthogonal axis, X, Y and Z respectively.
  • Electrode -Z is on the back of the torso, electrode +Z on the front, electrodes +X and
  • -X are on the sides of the torso and electrodes +Y and -Y at the top and bottom respectively of the torso.
  • a reference lead electrode (REF) is also used. Standard, pre-gelled, disposable
  • ECG electrodes are used.
  • the three channels (X, Y and Z) are recorded simultaneously in digital form.
  • a low noise, high gain, three channel ECG amplifier having a frequency band width from 0.1 to 1200 Hz and cross talk below -90dB is used for conditioning the ECG signals from electrode pairs.
  • Figure 11 shows such an amplifier.
  • Each channel is digitised at 4000 Hz with 16-bit resolution.
  • Each ECG digital recording is 7 or 11 megabytes In length, depending on the basic heart rate and the background noise during the recording.
  • Gain for each channel can be set independently at between 1000 and 20000 and the values noted for the later off-line processing.
  • a back-up record is made on a tape streamer. Off-line signal processing of each ECG is as follows.
  • Signal averaging is performed until the rms noise level during diastole is less than 0.3 microvolts.
  • Standard deviation of trigger jitter is estimated to be less than 0.2 milliseconds, provided that the rms noise level in the raw ECG is less than 40 microvolts.
  • the Single Fiducial Point (SFP) alignment technique is used (Escalona O.J. si 4l. , A fast and reliable beat alignment technique, Med. Bio. Eng & Comp., 29, Supp, 1991). Each beat is cross correlated with a template beat and was rejected for averaging if it was an ectopic beat. Excessively noisy beats with rms noise greater than 40 microvolts are also rejected.
  • High-pass filtering is performed digitally on each signal averaged lead.
  • a 40 Hz bidirectional 4th order Butterworth high-pass filter is used according to the standard method (Breithardt. G. si 4l- Standards for analysing of ventricular late potentials, Eur. Heart 0. (1991) 12, 473-480) to produce signals Xf, Y and If.
  • VLP Ventricular late potentials
  • start and end points are defined as follows.
  • the end point (VLP 0 f) for each signal is defined as the mid-point of a 5 milliseconds segment shifted along the ST segments towards the QRS complex in one millisecond steps until the mean voltage exceeds the mean noise level plus three times the standard deviation of noise sample (see Breithardt, above).
  • the terms QRS and ST are those regularly used for electrocardiograms.
  • the starting time of the VLP (t ) is defined on the vector magnitude combination of the three filtered orthogonal leads (Xf 2 + Y f 2 + lf 2 ) Vl , as the end-point ("right-hand" end) of a 5 milliseconds segment shifted from t ⁇ z into the QRS complex in one millisecond steps until its mean voltage exceeds 40 microvolts or has a peak value of 48 microvolts (i.e. 40 microvolts + 20%) to accommodate very brief peaking of the VLP vector magnitude.
  • VLP amplitude values are expressed in microvolt units and the VLP attractor is traced in the three dimensional voltage space with the X, Y, Z leads as the orthogonal axis ( ⁇ V3D space). (See Figures 4 and 5). Each point of the trace corresponds to a certain time between t 0 and t ⁇ z and has as co-ordinates the values of VLP amplitude of each corresponding filtered lead (X, Y, Z) at that particular time.
  • An important feature of the invention is the estimated fractal dimension ( ⁇ ) of the VLP attractor.
  • ⁇ log(L)/log(DD) where L is the total length of the trajectory of the attractor and DD is the spheric extent (maximum diameter) encompassing the attractor (both measured 1n microvolts).
  • the attractor trajectory (see Figures 4 and 5) is a discrete 3D curve in which points correspond to the sampling interval in each ECG lead recording (in one example 0.25 milliseconds).
  • the total length L 1s the sum of all the step distances between adjacent points in the curve. If there are N time steps each of 0.25 milliseconds between t 0 and t ⁇ then L 1s given by Equation 1 1n Figure 3.
  • the maximum diameter DD is obtained as follows. For every one of the N points on the curve the values of distance to each other (N-l) points is calculated. The absolute maximum of all the calculated distances is evaluated. The distance Dij between an 1th and a jth point 1n the attractor curve is given by Equation 2 in Figure 3. The matrix representation of all possible Dij elements, namely the distance matrix ⁇ , is equation 3 in Figure 3.
  • N has been found to be as large as 320 in some abnormal subjects (VLP duration of 80 milliseconds) and thus some abnormal subjects (VLP duration of 80 milliseconds).
  • Dij Dji, i.e. ⁇ is symmetrical. Accordingly the number of calculated distances can be halved if the process for DD is carried out on only the distance elements in the upper triangle of ⁇ . This is expressed as follows:
  • FIGS 4 and 5 show in convenient projections VLP attractors actually measured 1n accordance with the invention.
  • the values plotted are up to some tens of microvolts.
  • ⁇ calculated as above 1s shown on each Figure. Relating these Figures to Figure 1 the H/T axis (head/feet) corresponds to the +Y/-Y electrodes, the R/L axis (right side/left side) corresponds to the -X/+X electrodes and the F/B axis (torso front/torso back) corresponds to the +Z/-Z electrodes.
  • LAS40 longer than 38 milliseconds (Here fQRSd is the filtered QRS duration, RMS40 is the root mean square amplitude of the terminal 40 millisecond and LAS40 the duration of low amplitude signals (below 40 microvolts) in the vector magnitude QRS complex using 40 Hz high-pass bidirectional filtering.)
  • LP+ late potential positive
  • post - MI considered to be SCD+.
  • Figures 6a and 6b show results for a group of 45 persons believed healthy (regardless of whether they presented as normal VLP activity or not, mean age 38 ⁇ 8 years).
  • Figure 7 shows results for a group of 19 persons believed post-MI SCD+ and at risk (according to their medical history and having abnormal VLP activity according to the above standard analysis, mean age 58 ⁇ 12 years).
  • Column P# distinguishes the persons in each group, other columns are the above three conventional criteria while ⁇ is the fractal dimension calculated according to the invention.
  • the Figures include the mean value (MV) and standard deviation (SD).
  • Figure 8 shows the pooled variance (PV) and separated variance (SV) for a statistical Student t-test on the criteria results for the group in Figures 6a and 6b against the criteria results for the group in Figure 7.
  • the conventional criteria (RMS40, LAS40 and fQRSd) referred to above are from the time-domain of the electrode waveforms and depend on the algorithm used for detecting the onset and offset points of the filtered QRS complex. (This algorithm implements a standard definition given in Breithardt for the onset and offset points of the filtered QRS complex.) When micropotentials (less than 5 microvolts) are long delayed and with slow termination the algorithm is expected to err systematically, especially under noisy conditions. By using a parameter defined in the 3-D micro voltage space instead of the 2D voltage-time plane significant advantages are achieved. In the 3-D space curved behaviour depends only on voltage changes.
  • Apparatus to perform the invention can be arranged in any convenient form.
  • One arrangement is a specific electronic unit to which suitable signals are supplied and which carries out the attractor fractal dimension computation with suitably arranged electronic calculating devices to provide an indication on the unit or an associated display of the calculated fractal dimension for the supplied signals.
  • the ECG signal amplifiers described herein may be associated with or Incorporated 1n the apparatus if required.
  • the size of the sample shown in the tables of results is relatively small but is sufficient for an assessment of the clinical significance of ⁇ as an indicator (discriminator) of SCD+ in patients. Further a threshold value for ⁇ can be identified above by which a post-MI patient can be classified as SCD+.
  • a suggested basis for this value is the mean value of ⁇ in the group of persons believed healthy plus two times the standard deviation ( Figure 6). In this specific example this value is 1.337.
  • An alternative suggested basis for such a threshold value is the mean value of ⁇ for the group of persons believed healthy (1.2124) and ⁇ for the group of persons believed to be SCD+ (1.3737), this value of ⁇ SCD+ is 1.293.
  • the justification for this basis is the closeness of the standard deviation of ⁇ for the two groups shown, viz 0.062 and 0.054.
  • a value of ⁇ SC o + of 1.30 produces three false positives in the "healthy" group and one false negative in the "SCD+” group.
  • a canine model study provided more controlled conditions than possible with human patients.
  • "healthy” group there are some LP+ conditions while the post-MI group of Figure 7 includes cases which could have become completely healed.
  • This model study yielded smaller and closer deviations for the "healthy” and SCD+ groups (0.0411 and 0.0468 respectively). The smaller deviations reflected the more controlled conditions of the model study.
  • the above techniques show that it is likely that the fractal dimension of the VLP attractor 1n post-MI, SCD+ subjects is significantly higher than in "healthy” subjects, to the degree of 1 part 1n 1000 that this is not the case.
  • Figures 9 and 10 show the results of another technique according to an aspect of the invention for assessing VLP in which a discrete Hartley transform vector spectrum is used.
  • the spectrum amplitude components (A) are summed in two frequency ranges, -f ⁇ to -f 2 and +f 2 to +f- j , for example -300Hz to -60Hz and +60Hz to +300 Hz.
  • Figure 9 is an assessment for a person believed healthy and Figure 10 for a person believed SCD+. A higher value in the range of summed components for healthy and SCD+ persons indicates SCD+ risk. The higher value of summed components is believed to relate to increased complexity of the VLP and thus to SCD and condition.
  • FIG 11 is the circuit diagram of an ECG amplifier to enhance signal collection and useful in the practice of the present invention.
  • a three-operational amplifier front end FE has high early gain to minimise noise over a controlled bandwidth, for example 0.1 to 1200Hz and low crosstalk, below -90dB.
  • the amplifier for only one electrode pair, for example the x axis +E ⁇ and -E x supplying one channel X is shown for simplicity.
  • the gain/bandwidth control elements C g and R g are typically 10 ⁇ F to 1500 ⁇ F and 10 Q to 100Q respectively.
  • the values chosen for C g and R g set f c , the 3dB cut-off frequency, and a typical value for this in the above techniques is 0.14Hz.
  • the differential gain is determined by Rf and R g and the noise 1s related to the differential gain. Values of Rf above 1M ⁇ increase the noise significantly. A value of Rf around 300k ⁇ is a good compromise with C g at llOO ⁇ F and R g at 1 ⁇ . This enables the use of the minimum number of high-quality operational amplifiers while achieving high gain at low noise and resistance to interference from e.g. CRT scan frequencies and power freqencies such as 50 Hz, 60 Hz and their harmonics.
  • the front end (FE) is connected to a receiver (R) by a signal line SL of up to three to five meters.
  • the receiver also includes a regulated power supply (PSU) which supplies DC power to the receiver and via a similar length of power line PL, the front end where a DC/DC convertor provides appropriate voltages.
  • PSU regulated power supply
  • the receiver channel output, for example Ch X, is connected to a high pass filter.
  • the receiver gain is adjustable with a gain trim GT.

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  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Cardiology (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Molecular Biology (AREA)
  • Pathology (AREA)
  • Engineering & Computer Science (AREA)
  • Biomedical Technology (AREA)
  • Physics & Mathematics (AREA)
  • Medical Informatics (AREA)
  • Biophysics (AREA)
  • Surgery (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Veterinary Medicine (AREA)
  • Measurement And Recording Of Electrical Phenomena And Electrical Characteristics Of The Living Body (AREA)
  • Medical Treatment And Welfare Office Work (AREA)

Abstract

Un procédé d'analyse d'un potentiel ventriculaire tardif (PVT) consiste à déterminer un paramètre relatif à la complexité du PVT, paramètre important pour établir une évaluation clinique. Le procédé peut consister à calculer la dimension fractale de l'attracteur du PVT, laquelle constitue un paramètre destiné à établir une évaluation clinique. Le procédé peut également consister à effectuer une analyse spectrale produisant une évaluation basée sur un spectre vectoriel d'une transformée discrète de Hartley (TDH) par addition des composantes d'amplitude comprises entre -f1 à -f2 et +f2 à +f1, où f1 représente un nombre supérieur à f2.
EP94915662A 1993-05-21 1994-05-20 Analyse de formes d'ondes cardiaques Withdrawn EP0699323A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB939310604A GB9310604D0 (en) 1993-05-21 1993-05-21 Analysis of heart waveforms
GB9310604 1993-05-21
PCT/GB1994/001117 WO1994028494A1 (fr) 1993-05-21 1994-05-20 Analyse de formes d'ondes cardiaques

Publications (1)

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EP0699323A1 true EP0699323A1 (fr) 1996-03-06

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EP94915662A Withdrawn EP0699323A1 (fr) 1993-05-21 1994-05-20 Analyse de formes d'ondes cardiaques

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US (1) US5694942A (fr)
EP (1) EP0699323A1 (fr)
JP (1) JPH08510398A (fr)
GB (2) GB9310604D0 (fr)
IL (1) IL109721A (fr)
WO (1) WO1994028494A1 (fr)

Families Citing this family (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100010333A1 (en) * 2005-07-29 2010-01-14 Jorge Hernando Ordonez-Smith Bipolar, Non-Vectorial Electrocardiography
US6422998B1 (en) * 1999-09-20 2002-07-23 Ut-Battelle, Llc Fractal analysis of time varying data
JP3712350B2 (ja) * 2000-07-18 2005-11-02 独立行政法人科学技術振興機構 心室遅延電位の心臓磁界診断装置およびその作動方法
US6766189B2 (en) 2001-03-30 2004-07-20 Cardiac Pacemakers, Inc. Method and apparatus for predicting acute response to cardiac resynchronization therapy
US6993389B2 (en) 2001-03-30 2006-01-31 Cardiac Pacemakers, Inc. Identifying heart failure patients suitable for resynchronization therapy using QRS complex width from an intracardiac electrogram
US6705999B2 (en) * 2001-03-30 2004-03-16 Guidant Corporation Method and apparatus for determining the coronary sinus vein branch accessed by a coronary sinus lead
US6920349B2 (en) * 2002-07-01 2005-07-19 David M. Schreck System and method for predicting the onset of cardiac pathology using fractal analysis
US8602986B2 (en) * 2003-08-20 2013-12-10 Koninklijke Philips N.V. System and method for detecting signal artifacts
DE10351728A1 (de) * 2003-10-31 2005-06-30 W.O.M. World Of Medicine Ag Verfahren und System zur Diagnostik und/oder Überwachung des Herz-Kreislaufsystems eines Lebewesens
US7283864B2 (en) * 2005-02-10 2007-10-16 Cardiac Pacemakers, Inc. Method and apparatus for identifying patients with wide QRS complexes
US20070260151A1 (en) * 2006-05-03 2007-11-08 Clifford Gari D Method and device for filtering, segmenting, compressing and classifying oscillatory signals
US8321005B2 (en) * 2009-10-13 2012-11-27 Siemens Medical Solutions Usa, Inc. System for continuous cardiac pathology detection and characterization
CN103070681B (zh) * 2012-12-08 2016-08-03 太原理工大学 一种基于稀疏成分分析的心室晚电位分离方法

Citations (1)

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Publication number Priority date Publication date Assignee Title
US4478223A (en) * 1982-12-06 1984-10-23 Allor Douglas R Three dimensional electrocardiograph

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5341811A (en) * 1991-03-26 1994-08-30 Allegheny-Singer Research Institute Method and apparatus for observation of ventricular late potentials

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4478223A (en) * 1982-12-06 1984-10-23 Allor Douglas R Three dimensional electrocardiograph

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
GRASSBERGER/PROCACCIA: "Characterization of strange attractors.", PHYSICAL REVIEW LETTERS, vol. 50, no. 5, AMERICAN PHYSICAL SOC., pages 346 - 349 *
See also references of WO9428494A1 *

Also Published As

Publication number Publication date
GB2278686A (en) 1994-12-07
GB9410282D0 (en) 1994-07-13
WO1994028494A1 (fr) 1994-12-08
JPH08510398A (ja) 1996-11-05
GB9310604D0 (en) 1993-07-07
IL109721A0 (en) 1994-08-26
US5694942A (en) 1997-12-09
IL109721A (en) 1998-06-15

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